Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. A method performed by a user equipment (UE) in a wireless communication system, the method comprising: receiving, from a base station (BS), mobility assistance information informing the UE that conditional mobility is allowed, wherein the mobility assistance information includes information on candidate target cells for the conditional mobility; receiving, from the BS, a first threshold for a first target cell among the candidate target cells, a second threshold for a serving cell, a third threshold for the first target cell, and a fourth threshold for a second target cell among the candidate target cells; receiving a timer value including a first time period, where a handover to the first target cell may be not succeeded on the first target cell until the timer expires; measuring channel quality of the candidate target cells during the first time period; initiating a first random access procedure to a first target cell among the candidate target cells by transmitting a random access channel (RACH) preamble to the first target cell; initiating a handover to the first target cell as part of the first random access procedure, based on that a channel quality of the first target cell measured during the first time period is equal to or above the first threshold for the first target cell and a channel quality of the serving cell measured during the first time period is equal to or below the second threshold for the serving cell; during the first random access procedure after transmitting the RACH preamble to the first target cell: measuring channel quality of the candidate target cells during the first time period, based on the mobility assistance information; detecting that a channel quality of the second target cell measured during the first time period is greater than a channel quality of the first target cell measured during the first time period; and stopping the handover to the first target cell before detecting a failure of the handover to the first target cell, based on that the channel quality of the first target cell measured at the first time period is lower than the third threshold for the first target cell and the channel quality of the second target cell measured at the first time period is higher than the fourth threshold for the second target cell; and performing a second random access procedure to the second target cell by transmitting another RACH preamble to the second target cell based on contention free random access resources.
In wireless communication systems, user equipment (UE) must efficiently manage mobility to maintain reliable connections. A method for conditional mobility in a UE involves receiving mobility assistance information from a base station (BS), which includes a list of candidate target cells for potential handover. The UE also receives thresholds for evaluating channel quality: a first and third threshold for a first target cell, a second threshold for the serving cell, and a fourth threshold for a second target cell. Additionally, the UE receives a timer value defining a time period during which handover decisions are evaluated. During this period, the UE measures the channel quality of candidate target cells. If the first target cell's quality meets or exceeds its first threshold and the serving cell's quality falls below its second threshold, the UE initiates a random access procedure (RACH) to the first target cell. While this procedure is ongoing, the UE continues monitoring channel quality. If the second target cell's quality surpasses the first target cell's quality and the first target cell's quality drops below its third threshold while the second target cell's quality exceeds its fourth threshold, the UE aborts the handover to the first target cell before failure occurs. Instead, it initiates a contention-free RACH procedure to the second target cell. This method ensures dynamic and efficient handover decisions based on real-time channel conditions.
2. The method of claim 1 , wherein the information on candidate target cells includes at least one of cell identities of the candidate target cells, radio resource configuration information for the candidate target cells, and random access information for the candidate target cells.
This invention relates to wireless communication systems, specifically methods for managing handover procedures between cells in a cellular network. The problem addressed is the need for efficient and reliable handover of user devices (UEs) from a source cell to a target cell, minimizing service interruptions and improving network performance. The method involves transmitting information about candidate target cells to a user device during a handover process. This information includes at least one of the following: cell identities of the candidate target cells, radio resource configuration details for the candidate target cells, and random access information for the candidate target cells. The cell identities help the user device identify potential target cells, while the radio resource configuration information provides the necessary parameters for the user device to connect to the target cell. The random access information facilitates the initial synchronization and access procedure with the target cell, ensuring a smooth handover. By providing this information in advance, the method reduces the time and complexity of the handover process, improving the likelihood of a successful handover and minimizing disruptions to ongoing communications. This is particularly useful in scenarios where the user device may need to quickly switch between cells, such as in high-mobility environments or areas with dense cell coverage. The approach enhances network efficiency and user experience by streamlining the handover procedure.
3. The method of claim 2 , wherein the random access information for the candidate target cells includes at least one of time information, frequency information, preamble information, and beam information.
This invention relates to wireless communication systems, specifically methods for efficiently accessing target cells in a network. The problem addressed is the need for improved random access procedures to enhance connectivity and reduce latency when a device transitions between cells or establishes a new connection. The method involves determining random access information for candidate target cells, which includes at least one of time information, frequency information, preamble information, and beam information. This information is used to facilitate seamless and rapid access to the target cells. Time information specifies the timing resources available for random access, while frequency information indicates the frequency bands or channels designated for the procedure. Preamble information includes sequences or signals used to initiate the access process, and beam information defines the directional beams for beamformed communications, ensuring accurate signal transmission and reception. By incorporating these parameters, the method optimizes the random access process, reducing delays and improving reliability in wireless networks. This is particularly useful in scenarios where devices need to quickly switch between cells or establish connections in dynamic environments. The approach enhances overall network efficiency and user experience by minimizing interruptions and ensuring consistent connectivity.
4. The method of claim 1 , further comprising: receiving, from the BS, a value for counting a number of rejections of random access, wherein the number of rejections of random access from the first target cell reaches the value.
This invention relates to wireless communication systems, specifically improving random access procedures in cellular networks. The problem addressed is the inefficiency in handling repeated random access attempts when a user device (UE) fails to successfully connect to a target cell, leading to unnecessary signaling overhead and delays. The method involves a user device (UE) attempting random access to a first target cell in a wireless network. If the UE fails to establish a connection after a predefined number of attempts, it transitions to a second target cell for further access attempts. The UE monitors the number of rejections or failures during these attempts. Additionally, the UE receives a configurable threshold value from the base station (BS) that specifies the maximum allowed number of rejections before the UE must switch to the second target cell. This threshold ensures that the UE does not persist in failed attempts indefinitely, optimizing network resources and reducing latency. The method also includes the UE receiving updated parameters or instructions from the BS to adjust its behavior during the random access process, such as modifying the number of allowed retries or switching to a different cell. This dynamic adjustment helps adapt to varying network conditions and improves overall connection reliability.
5. The method of claim 1 , further comprising: receiving a timer from the BS, wherein the first random access procedure is not succeeded on the first target cell until the timer expires.
This invention relates to wireless communication systems, specifically improving random access procedures in cellular networks. The problem addressed is the inefficiency in handling failed random access attempts when a user device (UE) attempts to connect to a target cell but fails, leading to repeated attempts that waste resources and delay service. The method involves a user device performing a first random access procedure to connect to a first target cell. If this procedure fails, the device receives a timer from the base station (BS) that defines a waiting period before the device can attempt another random access procedure on the same target cell. The device must wait until this timer expires before retrying, preventing immediate repeated attempts that could overload the network. This timer-based approach ensures more orderly and efficient resource utilization, reducing unnecessary signaling and improving overall network performance. The method may also include additional steps such as receiving a second timer for a second target cell, allowing the device to prioritize or manage multiple connection attempts more effectively. The invention helps optimize network access by controlling retry behavior, particularly in scenarios where initial access attempts fail due to congestion or other issues.
6. The method of claim 1 , further comprising: determining the second target cell as a new target cell.
A system and method for wireless communication involves selecting and managing target cells in a network to optimize connectivity and performance. The technology addresses challenges in maintaining stable and efficient communication links in dynamic wireless environments, such as handover delays, signal interference, and resource allocation inefficiencies. The method includes identifying a first target cell for communication based on signal strength, load balancing, or other criteria. Additionally, the method determines a second target cell as a new target cell, which may involve reassessing network conditions, user device mobility, or changes in network topology. This step ensures continuous optimization of the communication path by dynamically adjusting target cells to adapt to real-time conditions. The process may involve evaluating multiple parameters, such as signal quality, latency, and network congestion, to select the most suitable target cell. By incorporating this dynamic selection, the system enhances reliability, reduces handover failures, and improves overall network efficiency. The method is particularly useful in scenarios where user devices move frequently or where network conditions fluctuate, ensuring seamless connectivity and performance.
7. A user equipment (UE) configured to perform a handover in a wireless communication system, the UE comprising: a transceiver; at least one processor; and at least one computer memory operably connectable to the at least one processor and storing instructions that, when executed, cause the at least one processor to perform operations comprising: receiving, from a base station (BS), mobility assistance information informing the UE that conditional mobility is allowed, wherein the mobility assistance information includes information on candidate target cells for the conditional mobility; receiving a timer value including a first time period, where a handover to the first target cell may be not succeeded on the first target cell until the timer expires; measuring channel quality of the candidate target cells during the first time period; receiving, from the BS, a first threshold for a first target cell among the candidate target cells, a second threshold for a serving cell, a third threshold for the first target cell, and a fourth threshold for a second target cell among the candidate target cells; initiating a first random access procedure to a first target cell among the candidate target cells by transmitting a random access channel (RACH) preamble to the first target cell; initiating a handover to the first target cell as part of the first random access procedure, based on that a channel quality of the first target cell measured during the first time period is equal to or above the first threshold for the first target cell and a channel quality of the serving cell measured during the first time period is equal to or below the second threshold for the serving cell; during the first random access procedure after transmitting the RACH preamble to the first target cell: measuring channel quality of the candidate target cells during the first time period, based on the mobility assistance information; detecting that a channel quality of the second target cell measured during the first time period is greater than a channel quality of the first target cell measured during the first time period; and stopping the handover to the first target cell before detecting a failure of the handover to the first target cell, based on that the channel quality of the first target cell measured at the first time period is lower than the third threshold for the first target cell and the channel quality of the second target cell measured at the first time period is higher than the fourth threshold for the second target cell; and performing a second random access procedure to the second target cell by transmitting another RACH preamble to the second target cell based on contention free random access resources.
In wireless communication systems, user equipment (UE) must efficiently manage handover between cells to maintain connectivity. A key challenge is ensuring seamless transitions while avoiding unnecessary handovers or failures. This invention addresses this by enabling conditional mobility, where a UE can dynamically switch target cells during a handover procedure based on real-time channel quality measurements. The UE receives mobility assistance information from a base station (BS), including candidate target cells and a timer value defining a time period for evaluating handover conditions. During this period, the UE measures channel quality of the candidate cells. The BS provides thresholds for the serving cell and target cells, including a first threshold for initiating handover to a first target cell and a second threshold for the serving cell. If the first target cell's quality meets or exceeds its threshold while the serving cell's quality falls below its threshold, the UE initiates a handover by transmitting a random access channel (RACH) preamble. During the handover, the UE continues monitoring channel quality. If it detects that a second target cell's quality surpasses the first target cell's quality, the UE may abort the ongoing handover if the first target cell's quality drops below a third threshold and the second target cell's quality exceeds a fourth threshold. The UE then initiates a new handover to the second target cell using contention-free RACH resources, ensuring efficient and adaptive mobility decisions. This approach minimizes handover failures and improves network performance.
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August 25, 2020
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